Backhoe swing mechanism



March 4, 1969 H. A. M LAUGHLIN BACKHOE SWING MECHANISM Sheet Filed March 50, 1967 NVENTOR M ZRIIG/VZ/IU ATTORNEY March 4, 1969 H. A. M LAUGHLIN BACKHOE SWING MECHANISM Sheet 2 of Filed March 30, 1967 ATTOR NEY March 4, 1969 H. A. M LAUGHLI'N 3,430,503

BACKHOE SWING MECHANISM Filed March 30, 1967 Sheet of I NVEN TOR A4919? y 14. M MUGIyZ/A/ BY ATTORNEY United States Patent Office Claims ABSTRACT OF THE DISCLOSURE A backhoe swing mechanism comprises a pair of double acting hydraulic cylinders mounted on the main frame and linkage connecting each cylinder with the swing frame. Each connecting linkage consists of a first link pivoted to the main frame and a second link extending between the first link and the swing frame.

This invention relates to tractor-mounted backhoes and more particularly to a swing mechanism for swinging a backhoe boom from side to side.

Tractor-mounted backhoes usually comprise a main frame attached to or permanently built into the rear of the tractor. A swing frame, from which the backhoe boom is supported, is mounted on the main frame on a vertical pivot and may be swung to either side through a total angle of approximately 180. The swing mechanism conventionally is powered by hydraulic cylinders cont-rolled by the backhoe operator by means of manually operated hydraulic control valves.

According to the present invention, the hydraulic cylinders of the swing mechanism are double-acting and are linked to the swing frame by an improved linkage that permits both cylinders to provide the power for swinging the backhoe, the geometry of the links being such that the rotary force transmitted to the swing frame by each cylinder is more or less constant throughout the entire range of swing of the swing from side to side.

In the form shown of the present invention, this is accomplished by a pair of C-shaped links pivoted to the main frame by a common pivot laterally centered on the main frame and a second pair of links connecting t-hese swinging links to a common pivot on the swing frame. The ends of the cylinder rods are connected to the C- shaped links for transmitting power of both cylinders in swinging the swing frame in either direction.

Among the objects of the present invention are to provide an improved backhoe swing frame construction in which double-acting hydraulic cylinders are linked to the swing frame by an improved linkage providing a more or less uniform rate of swing throughout the entire range of swinging movement, to provide such a mechanism in which both cylinders supply power for swinging the backhoe in either direction, to provide such a mechanism which is economical, simple and durable, and generally to improve backhoe swing mechanisms of the type described.

Other objects and objects relating to details and economies of manufacture will be more apparent from the detailed description to follow.

My invention is clearly defined in the appended claims. In the claims, as well as in the description, parts may at times be identified by specific names for clarity and convenience, but such nomenclature is to be understood as having the broadest meaning consistent with the context and with the concept of my invention as distinguished from the pertinent prior art. The best form in which I have contemplated applying my invention is illustrated in the accompanying drawings forming a part of this specification in which:

FIGURE 1 is a top plan view of the backhoe swing mechanism and associated parts, a portion of the main Patented Mar. 4, 1969 frame, swing frame and boom being broken away or shown in section and the hydraulic hoses being omitted.

FIGURE 2 is a perspective view of the backhoe swing mechanism and associated parts, portions of the main frame, stabilizer, boom and lift cylinder being broken away.

FIGURE 3 is a perspective view of the underside of the backhoe swing mechanism and associated parts, portions of the main frame and boom being broken away.

FIGURE 4 is a side elevation of the swing mechanism and associated parts, portions of the main frame, hydraulic hoses, boom and lift cylinder being broken away.

Referring now to the drawings, the swing mechanism of the present invention is shown applied to a tractor-mounted backhoe having a main frame 10 which may be permanently built onto the rear of an industrial type tractor or may be a separate unit attached thereto. The main frame usually is located at the rear of the tractor between the rear wheels. The main frame 10 is provided with conventional stabilizing arms (not shown) projecting laterally from each side of the main frame and forced by hydraulic cylinders into contact with the ground when the backhoe is being used. A hydraulic cylinder 11 for one stabilize-r is shown in FIGURE 2.

A swing frame 12 is pivotally mounted on the vertical axis on the center rear of the main frame 10 by a pair of co-axial pivot pins 14 and 15. The swing frame 12 supports a backhoe boom 16 on a horizontal pivot pin 17 and a lift cylinder 19 by means of a horizontal pivot pin 20. The lift cylinder 19 is connected to the upper portion of the boom 16 for raising and lowering the boom by rocking it about its pivot pin 17. The construction described in the detailed description above is generally conventional and does not form a part of this invention.

A pair of hydraulic cylinders 21 are pivotally mounted on U-shaped frame members 22 of the main frame 10, the closed end 24 of each cylinder being pivotally mount ed by a vertical pin 25 permitting limited oscillation of the cylinders in a horizontal plane. The cylinders 21 are double-acting and hydraulic hoses 26 connect the cylinders with a manually-operated hydraulic control valve (not shown). The piston rods 27 of the cylinders project rearwardly of the tractor and lie one on each side of the pivot axis of the swin frame 12.

The free ends of the piston rods 27 are connected to the main frame 10 and swing frame 12 by a linkage including a pair of swinging links 29 pivotally mounted on the main frame and a pair of links 30 connecting the links 29 with the swing frame 12. The swinging links 29, which lie generally in a common horizontal plane, are C-shaped to provide clearance about the portion of the swing frame 12 surrounding the pivot pin 15. Preferably, the links 29 are pivotally mounted on the main frame 10 by a single vertical pivot pin 31.

The links 30, which connect the free ends of the links 29 to the swing frame 12, are pivotally mounted on the swing frame by a common vertically-extending pivot pin 32. The pivot pins 31 and 32 preferably are laterally centered on the main frame 10 and swing frame 12 respectively (see FIGURE 1) and are diametrically opposite when the boom 16 extends to the rear.

The links 29 and 30 are interconnected by pivot pins 34, the adjacent ends of the links 29 preferably being bifurcated to receive the ends of the links 30. Preferably, the pivot pins 31, 32 and 34 are provided with fixed projecting ears 35 welded to the pins and receiving a bolt 36 which holds the pin in place and serves to prevent rotation of the pin in the supporting link.

The free ends of the piston rods 27 are pivotally connected to the links 29 intermediate their ends by verticallyextending pivot pins 37, which are held in position by ears 35 and bolts 36 similar to the pins previously described.

3 As will be seen in FIGURE 1, the pivot pins 37 are located in the portions of the C-shaped links 29 most remote from the swing frame axis when the swing frame and boom are extended to the rear of the tractor.

In operation, when the backhoe is swung, one of the double-acting cylinders 11 extends and the other retracts. The backhoe swing linkage, including the links 29 and 30, permits both extending and retracting action of the cylinders to be communicated to the swing frame, thus more nearly balancing shear forces on the pivot pins 14 and 15. When the swing frame 12 is swung all the way to one side, the C-shaped link 29 on the opposite side extends closely about, but does not touch the portion of the swing frame surrounding the pivot pin 20.

The swing linkage above described provides a more nearly uniform mechanical advantage in the connection between the double-acting cylinders 11 and the swing frame 12, thus providing a generally uniform rate of swinging movement of the swing frame throughout the entire range of swinging movement. This provides a more or less uniform swinging force throughout the entire range of swinging movement of the backhoe and facilitates accurate control of such swinging movement so as to facilitate quickly and accurately positioning the backhoe for return to trench.

What is claimed is:

1. In a tractor-mounted backhoe, a main frame carried by the tractor, a swing frame mounted for horizontal swinging movement above a fixed vertical pivot on the main frame, a pair of double-acting hydraulic cylinders pivotally mounted for horizontal swinging movement on the main frame and having piston rods projecting one on each side of the pivot of the swing frame, and linkages connecting the end of each piston rod to swing the swing frame, each of said linkages comprising a first link having an end mounted on the main frame for horizontal swinging movement, a second link interconnecting said first link and the swing frame and the piston rod end being connected to one of said links, whereby operation of the cylinders to retract one cylinder and extend the other will swing the swing frame about its pivot.

2. In a tractor-mounted backhoe as claimed in claim 1, the first links being pivotally connected to the main frame by a single common pivot pin laterally centered with respect to the main frame.

3. In a tractor-mounted backhoe as claimed in claim 2, the second links being pivotally connected to the swing frame by a single common pivot pin laterally centered with respect to the swing frame.

4. In a tractor-mounted backhoe as claimed in claim 1, the second link being pivotally connected to the swing frame by a single common pivot pin laterally centered with respect to the swing frame.

5. In a tractor-mounted backhoe as claimed in claim 3, the first links being C-shaped and opening towards the swing frame pivot to provide clearance for swinging the swing frame through an angle of about in either direction.

References Cited UNITED STATES PATENTS 2,528,985 11/1950 Wunsch 212-66 3,042,236 7/1962 Pilch 212-66 X 3,343,686 9/1967 Bjerkan 2l266 ROBERT A. OLEARY, Primary Examiner.

WILLIAM E. WAYNER, Assistant Examiner.

US. Cl. X.R; 

